pdfresurrect 0.15 - Buffer Overflow

2019-07-26 12:17:48

# Exploit Title: pdfresurrect 0.15 Buffer Overflow
# Date: 2019-07-26
# Exploit Author: j0lama
# Vendor Homepage: https://github.com/enferex/pdfresurrect
# Software Link: https://github.com/enferex/pdfresurrect
# Version: 0.15
# Tested on: Ubuntu 18.04
# CVE : CVE-2019-14267


PDFResurrect 0.15 has a buffer overflow via a crafted PDF file because
data associated with startxref and %%EOF is mishandled.

Additional Information

There is a buffer overflow in pdfresurrect 0.14 caused by a malicious
crafted pdf file.

In function pdf_load_xrefs at pdf.c file, it counts how many times the
strings '%%EOF' appear in the pdf file. Then for each xref the code
starts to rewind incrementing the pos_count variable until found a 'f'
character (the last character of the 'startxref' string). Then these
bytes between the 'f' and '%%EOF' will be read with the 'fread'
function and copied to a 256 char buffer. The 'pos_count' variable
tells 'freads' how many bytes has to copy. If malicious user crafted a
pdf file with more that 256 bytes between '%%EOF' and the immediately
previous 'f' then a buffer overflow will occur overwriting everything
after the 'buf' buffer.

In the code:
int pdf_load_xrefs(FILE *fp, pdf_t *pdf)
int i, ver, is_linear;
long pos, pos_count;
char x, *c, buf[256];

c = NULL;

/* Count number of xrefs */
pdf->n_xrefs = 0;
fseek(fp, 0, SEEK_SET);
while (get_next_eof(fp) >= 0)

if (!pdf->n_xrefs)
return 0;

/* Load in the start/end positions */
fseek(fp, 0, SEEK_SET);
pdf->xrefs = calloc(1, sizeof(xref_t) * pdf->n_xrefs);
ver = 1;
for (i=0; i<pdf->n_xrefs; i++)
/* Seek to %%EOF */
if ((pos = get_next_eof(fp)) < 0)

/* Set and increment the version */
pdf->xrefs[i].version = ver++;

/* Rewind until we find end of "startxref" */
pos_count = 0;
while (SAFE_F(fp, ((x = fgetc(fp)) != 'f'))) <== The loop will continue incrementing pos_count until find a 'f' char
fseek(fp, pos - (++pos_count), SEEK_SET);

/* Suck in end of "startxref" to start of %%EOF */
memset(buf, 0, sizeof(buf));
SAFE_E(fread(buf, 1, pos_count, fp), pos_count, <== If pos_count > 256 then a buffer overflow occur
"Failed to read startxref.\n");
c = buf;
while (*c == ' ' || *c == '\n' || *c == '\r')

/* xref start position */
pdf->xrefs[i].start = atol(c);

This is a crafted PDF that produces a buffer overflow:



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